What is the best technique to remove SMD ICs ?

[pfuentes69]

Hey.
I want to make some 4MB 30 pin SIMMs for fun and the only source I could find for the appropriate memory chips are from 16MB or 32MB SIMMs.
I plan to remove the chips using my cheap hot air gun, but I never did such thing. What is the right technique? (Temperature, time to apply heat, distance…)
Thanks!

 

[TallyFeli]

Hi....Its uncommon to need to save *BOTH* the chip *AND* the board - the typical situation is needing to eliminate a failure chip from one board and rescue its substitution from another.

The simplest method for moving the failure chip, is to shear every one of the pins flush with the header. A tough art blade is convenient for this as long as you take care not to cut into any tracks under.

The giver PCB will not be a lot of utilization without the chip you're taking off it - I heat the opposite side with a modeler's pencil blowtorch, certain individuals simply place the board on a hot plate.

Assuming you're that frantic to move the failure chip without harming it, you could utilize a hot compressed air firearm as others have recommended - yet a hot compressed air firearm can undoubtedly burn the PCB if you don't watch out.

I've singed a couple of sheets that way, and more than once I pulled off blowtorching with no burning - a ton relies upon the nature of the PCB material.

 

[pfuentes69]

Thanks. In this case the idea is to remove the chips to reuse in a different board.

In fact I went ahead and tried this last weekend. I started with the heat gun at 300C but it was too slow, so I went up to 360C and I could remove the chips easily.

Now I just hope I didn’t damage the chips…

 

[max1zzz]

You'll have no problem removeing chips at 360C unless you linger with the hot air for a really really long time, I have been known to use 450C before and haven't killed a chip yet! (450C will easily damage older boards though so I wouldn't recommend it!)

 

[trag]

Others will undoubtedly have other, possibly better methods. When I've removed chips from existing SIMMs what I've done is supported the SIMM an inch or so above the surface in an upside down position -- chips hanging from the bottom.

(If you have chips on both sides, beats me. Support it vertically? Clamp it by edge connector and suspend?)

Then heat the top, holding the heat source with one hand and have a dental pick or similar tool available in the other hand. Use the pick-tool to gently pry the chips off the board as the solder melts.

Often the pick isn't needed, but the surface tension from melted solder can hold the chips against gravity sometimes.

For supporting the SIMMs, I built a couple of little pedestals out of modeling clay.

The last time I did this was about 15 years ago and at that time I didn't have a hot-air rework station, just a Milwaukee heat gun with a dial labeled 1 - 9. I think I used something like the 8 setting. I might have seen one failed memory chip out of a couple of hundred, but then, I don't know that the SIMMs were in perfect working condition before I started.

 

[pfuentes69]

Thanks, these tips will help for next time.

I’ll receive soon the PCB and then the next challenge will be to solder back the chips… I never did this type, with the legs twisted to the inside.

 

[trag]

Forgot to mention, it is always helpful to apply solder flux to the joints before these operations.

 

[davidg5678]

I would recommend that you use low-melt solder. It is a special kind of solder alloy that stays liquid for a long time, which means that you can apply it to all the legs of the smd chip, and remove the IC while both sides of the chip's solder are liquid. This method uses minimal heat, so it should have a high chance of success. There are some great videos of it on YouTube, if you want to see it in action.

 

[Fizzbinn]

I would recommend that you use low-melt solder. It is a special kind of solder alloy that stays liquid for a long time, which means that you can apply it to all the legs of the smd chip, and remove the IC while both sides of the chip's solder are liquid. This method uses minimal heat, so it should have a high chance of success. There are some great videos of it on YouTube, if you want to see it in action.

I second this approach, especially if you are trying to do this with a just an iron. I’ve have good results using ChipQuik:

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